This invention relates to solving problems in laser printers, copiers and facsimile machines, known as imaging machines, involving poor print quality. The problem actually occurs in a high percentage of toner cartridges that are used in the imaging machines. The major printer manufacturers include the popular HP Series 2 and Series 3 LASERJET series SX printers as well as some APPLE, QMS, CANON, and BROTHER SX printers. At the time of this writing, this SX printer is the most widely used printer worldwide, but its numbers are diminishing because the OEM manufacturers discontinued manufacturing it over three years ago. However, the numbers are so high that these SX printers will still be numerous for quite some time to come. For example, there are over 200 million SX toner cartridges out in the field since the printer first was released.
CANON has designed an all-in-one cartridge as in U.S. Pat. No. 4,975,744, issued Dec. 4 1990 and assigned to CANON. Several companies have used similar cartridges in laser printers, copy machines and facsimile machines, each with the varying printer engines and a different nameplate. Originally, these cartridges were designed to be "disposable". However, after the first all-in-one toner cartridge was introduced, it did not take long before laser cartridge remanufacturers began remanufacturing cartridges. These "disposable" cartridges were designed to function for only one cartridge cycle without remanufacturing. The remanufacturers had found certain components that needed replacement on a regular basis. In 1990, the first aftermarket photoreceptor drum became available for use in remanufacturing the all-in-one toner cartridge of the "SX" engine variety, the most popular printer cartridge from around 1987 through 1995 at the time of this writing. When the long-life photoreceptor drum became available, the entire remanufacturing industry turned around and gained great strength and began a huge growth surge that still continues. In October 1993, HEWLETT-PACKARD, the largest seller of this printer engine using the all-in-one cartridge, entered the cartridge remanufacturing industry with the "OPTIVA" cartridge, further increasing the size as well as credibility of this relatively new industry, although OPTIVA has since been discontinued. However, this relatively new industry grew from the all-in-one cartridge shortly after its debut. Before the introduction of the long-life drum, sometimes called the "superdrum" or "duradrum", the SX cartridge would last for around three cartridge remanufacturing cycles at best, since the maximum useful life of the OEM drum was three cycles. However, the long-life drums got their names from the fact that they were designed to last for many remanufacturing cycles or recharges as they are sometimes called. Typically, the long life drum can last for ten or more such cycles, unlike the typical OEM(Original Equipment Manufacturer) drum. With the additional developments of drum coatings, originally designed for OEM drums, the long-life drum may last for many additional cycles. Some coatings, in theory, were designed to be dissolved and removed from over the drum surface every 1-3 cycles, so the drum life of the long-life drum almost seems limitless.
However, with photoreceptor drums lasting for many cycles, other components of the cartridge have a tendency to require greater durability, a better solution, or a greater life. Also, as the success of these cartridges has skyrocketed, the demand is for cartridges with longer cycles, so component improvements are significant. Therefore, avoiding natural problems with prevention means must also be implemented for cartridges of longer life both in longer cycle times and greater number of cycles. There is an inherent set of problems within the SX toner cartridge more specifically located in the toner hopper assembly.
First, "gapping" is required to properly install the doctor blade. This gapping takes extra time and is an inconvenience when remanufacturing the toner cartridge. Consequently, the toner cartridge remanufacturer may prefer a toner cartridge that does not require gapping whereas the OEM manufacturer may prefer a toner cartridge that does require gapping because of the deterrent it creates for remanufacturers.
Second, uneven and cloudy gray scales and solid black fills on the printed output paper often result from using the SX doctor blade. Third, the SX doctor blade, by scraping the toner, puts a strain on the rotation of the developer roller. Fourth, the doctor blade has to be adjusted in position to prevent variation in gap width between the metering edge of the doctor blade and the roller. When not properly adjusted, banding or uneven darkness of the print may occur on the output paper. Finally, the open cell foam that is required under the doctor blade to prevent toner leakage out of the toner hopper loses its resilience after time and fails to prevent toner leakage. Additionally, with a developer roller that turns easier, there is less pressure on the developer roller felt bearings and plastic spacer bushings and thus, leakage from the ends may be minimized. Applicant has U.S. Pat. No. 5,296,902 on a long-life design for these felt end bearings.
There is a need for a spreader blade usable in the SX toner hopper in place of the SX doctor blade which does not require gapping or adjusting, does not cause uneven solid printing, does not resist the rotation of the developer roller, and prevents toner leakage from beneath the blade without the need for open cell foam. Modifying the SX doctor blade to operate as a spreader blade would provide a simple, cost-effective solution to all the problems associated with the conventional SX doctor blade.